Multi-version database concurrency control system based on fragment-free collection

Abstract

The invention provides a database multi-version concurrency control system based on fragment-free recovery, which includes a transaction information recording module, a transaction data management module, a data visibility optimization module, a memory optimization speed-up module and a multi-version recovery module. The present invention utilizes the file group of fixed-length file or the way of fixed-length logical segment to design the rollback segment, provides a set of MVCC implementation mechanism and the method of rollback segment recycling and cleaning, and improves the access response time in combination with memory access optimization, thereby avoiding It avoids significant system overhead caused by rollback segment recycling, and avoids disk fragmentation; at the same time, the configurable rollback segment can ensure that there is no limit to the number of concurrently running transactions and the length of the transaction if there are enough disks; In addition, the combined design of memory and disk can meet the requirements of avoiding or reducing disk access in most cases, so as to ensure the access performance of the system.

Description

technical field [0001] The invention relates to the technical field of system optimization, in particular to a database multi-version concurrency control system based on fragment-free recovery. Background technique [0002] When traditional databases support concurrent transaction access, they usually provide different data access isolation levels to meet the application's use of data. At present, there are two main implementation methods: transaction lock-based mechanism and multi-version concurrency control mechanism. The biggest disadvantage of the former is that there will be mutual exclusion of read and write, which will reduce the concurrency of the system. So the latter has gradually become the current mainstream implementation. The principle is to add a new data version to the back of the data structure when data is changed or deleted, and to retain the original version of the data version in the system. At the same time, each time data is generated, an incrementa...

AI Technical Summary

Problems solved by technology

In practice, these recycling processes will bring additional CPU overhead, disk read and write operations, and memory operations. During the triggering process of recycling operations, the system processing capacity will be greatly affected, and the stability will be greatly reduced.

After recycling, it will also cause disk fragmentation, which reduces the efficiency of disk access

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